The writer of the "Itsy Bitsy Teeny-Weeny Yellow Polka-Dot Bikini" single, Paul Vance, based it on his young daughter's reluctance to be seen in public in said bikini. (And yes, that WAS "itsy-bitsy" for its time.)
TRANSCRIPTION COURTESY OF JOSEPH HOUK - CASSIE'S BUCKET LIST "#12 – Meet the girl who wore that itsy-bitsy teeny-weeny yellow polka dot bikini."  (Bikini Girl) "I feel so... uncomfortable..." (CW) "Don't worry, sweetie, you'll get used to it. Just wait 'til you get older!" (to herself) "...and the bikinis get even teenier!!!"